public Layer(Matrix weightMatrix, Vector biasVector, ActivationFunction af) {
activationFunction = af;
this.weightMatrix = weightMatrix;
lastWeightUpdateMatrix = new Matrix(weightMatrix.getRowDimension(),
weightMatrix.getColumnDimension());
penultimateWeightUpdateMatrix = new Matrix(weightMatrix
.getRowDimension(), weightMatrix.getColumnDimension());
this.biasVector = biasVector;
lastBiasUpdateVector = new Vector(biasVector.getRowDimension());
penultimateBiasUpdateVector = new Vector(biasVector.getRowDimension());
}